# Statistical Skills AQA AS Level Geography (unit 2)

The AQA specification requires you to know

â€¢ measures of central tendency â€“ mean, mode,

median

â€¢ measures of dispersion â€“ interquartile range and

standard deviation

â€¢ Spearmanâ€™s rank correlation test

Here is a simple explanation of them all.

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• Created by: Annie
• Created on: 28-05-12 10:40

## Pages in this set

### Page 1

Geography Skills Paper
Interquartile Range
Step 1: Put the numbers in order
1,2,5,6,7,9,12,15,18,19,27
Step 2: Find the median (How to find a median)
1,2,5,6,7,9,12,15,18,19,27
Step 3: Find Q1 and Q3
Q1 can be thought of as a median in the lower half of the data, and Q3 can be thought…

### Page 2

Median: Put them in order then it is `the middle value': if there are an even number of values
then take the middle two values and divide them by 2.
Spearman's Rank: Spearman's rank correlation coefficient allows you to identify easily the
strength of correlation within a data set of…

### Page 3

4. Work out the differences between the ranks (if rank 1=1 and rank 2=2 then the difference
would be 1).

5. Square the differences.

6. Add up all results in the d squared column: eg. This would become

7. Put this result into the Spearmans rank coefficient formula e.g.

8.…

### Page 4

9. Interperet your results: your result WILL vary between 1 and 1 if you have done you
calculation correctly:
Close to 1= Negative correlation
Close to 0= No linear correlation
Close to 1= Positive correlation